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Diffstat (limited to 'contrib/llvm/lib/CodeGen/LiveRangeCalc.h')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/LiveRangeCalc.h | 298 |
1 files changed, 298 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/LiveRangeCalc.h b/contrib/llvm/lib/CodeGen/LiveRangeCalc.h new file mode 100644 index 000000000000..9f226b154a67 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/LiveRangeCalc.h @@ -0,0 +1,298 @@ +//===- LiveRangeCalc.h - Calculate live ranges ------------------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// The LiveRangeCalc class can be used to compute live ranges from scratch. It +// caches information about values in the CFG to speed up repeated operations +// on the same live range. The cache can be shared by non-overlapping live +// ranges. SplitKit uses that when computing the live range of split products. +// +// A low-level interface is available to clients that know where a variable is +// live, but don't know which value it has as every point. LiveRangeCalc will +// propagate values down the dominator tree, and even insert PHI-defs where +// needed. SplitKit uses this faster interface when possible. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_LIB_CODEGEN_LIVERANGECALC_H +#define LLVM_LIB_CODEGEN_LIVERANGECALC_H + +#include "llvm/ADT/ArrayRef.h" +#include "llvm/ADT/BitVector.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/IndexedMap.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/CodeGen/LiveInterval.h" +#include "llvm/CodeGen/MachineBasicBlock.h" +#include "llvm/CodeGen/SlotIndexes.h" +#include "llvm/MC/LaneBitmask.h" +#include <utility> + +namespace llvm { + +template <class NodeT> class DomTreeNodeBase; +class MachineDominatorTree; +class MachineFunction; +class MachineRegisterInfo; + +using MachineDomTreeNode = DomTreeNodeBase<MachineBasicBlock>; + +class LiveRangeCalc { + const MachineFunction *MF = nullptr; + const MachineRegisterInfo *MRI = nullptr; + SlotIndexes *Indexes = nullptr; + MachineDominatorTree *DomTree = nullptr; + VNInfo::Allocator *Alloc = nullptr; + + /// LiveOutPair - A value and the block that defined it. The domtree node is + /// redundant, it can be computed as: MDT[Indexes.getMBBFromIndex(VNI->def)]. + using LiveOutPair = std::pair<VNInfo *, MachineDomTreeNode *>; + + /// LiveOutMap - Map basic blocks to the value leaving the block. + using LiveOutMap = IndexedMap<LiveOutPair, MBB2NumberFunctor>; + + /// Bit vector of active entries in LiveOut, also used as a visited set by + /// findReachingDefs. One entry per basic block, indexed by block number. + /// This is kept as a separate bit vector because it can be cleared quickly + /// when switching live ranges. + BitVector Seen; + + /// Map LiveRange to sets of blocks (represented by bit vectors) that + /// in the live range are defined on entry and undefined on entry. + /// A block is defined on entry if there is a path from at least one of + /// the defs in the live range to the entry of the block, and conversely, + /// a block is undefined on entry, if there is no such path (i.e. no + /// definition reaches the entry of the block). A single LiveRangeCalc + /// object is used to track live-out information for multiple registers + /// in live range splitting (which is ok, since the live ranges of these + /// registers do not overlap), but the defined/undefined information must + /// be kept separate for each individual range. + /// By convention, EntryInfoMap[&LR] = { Defined, Undefined }. + using EntryInfoMap = DenseMap<LiveRange *, std::pair<BitVector, BitVector>>; + EntryInfoMap EntryInfos; + + /// Map each basic block where a live range is live out to the live-out value + /// and its defining block. + /// + /// For every basic block, MBB, one of these conditions shall be true: + /// + /// 1. !Seen.count(MBB->getNumber()) + /// Blocks without a Seen bit are ignored. + /// 2. LiveOut[MBB].second.getNode() == MBB + /// The live-out value is defined in MBB. + /// 3. forall P in preds(MBB): LiveOut[P] == LiveOut[MBB] + /// The live-out value passses through MBB. All predecessors must carry + /// the same value. + /// + /// The domtree node may be null, it can be computed. + /// + /// The map can be shared by multiple live ranges as long as no two are + /// live-out of the same block. + LiveOutMap Map; + + /// LiveInBlock - Information about a basic block where a live range is known + /// to be live-in, but the value has not yet been determined. + struct LiveInBlock { + // The live range set that is live-in to this block. The algorithms can + // handle multiple non-overlapping live ranges simultaneously. + LiveRange &LR; + + // DomNode - Dominator tree node for the block. + // Cleared when the final value has been determined and LI has been updated. + MachineDomTreeNode *DomNode; + + // Position in block where the live-in range ends, or SlotIndex() if the + // range passes through the block. When the final value has been + // determined, the range from the block start to Kill will be added to LI. + SlotIndex Kill; + + // Live-in value filled in by updateSSA once it is known. + VNInfo *Value = nullptr; + + LiveInBlock(LiveRange &LR, MachineDomTreeNode *node, SlotIndex kill) + : LR(LR), DomNode(node), Kill(kill) {} + }; + + /// LiveIn - Work list of blocks where the live-in value has yet to be + /// determined. This list is typically computed by findReachingDefs() and + /// used as a work list by updateSSA(). The low-level interface may also be + /// used to add entries directly. + SmallVector<LiveInBlock, 16> LiveIn; + + /// Check if the entry to block @p MBB can be reached by any of the defs + /// in @p LR. Return true if none of the defs reach the entry to @p MBB. + bool isDefOnEntry(LiveRange &LR, ArrayRef<SlotIndex> Undefs, + MachineBasicBlock &MBB, BitVector &DefOnEntry, + BitVector &UndefOnEntry); + + /// Find the set of defs that can reach @p Kill. @p Kill must belong to + /// @p UseMBB. + /// + /// If exactly one def can reach @p UseMBB, and the def dominates @p Kill, + /// all paths from the def to @p UseMBB are added to @p LR, and the function + /// returns true. + /// + /// If multiple values can reach @p UseMBB, the blocks that need @p LR to be + /// live in are added to the LiveIn array, and the function returns false. + /// + /// The array @p Undef provides the locations where the range @p LR becomes + /// undefined by <def,read-undef> operands on other subranges. If @p Undef + /// is non-empty and @p Kill is jointly dominated only by the entries of + /// @p Undef, the function returns false. + /// + /// PhysReg, when set, is used to verify live-in lists on basic blocks. + bool findReachingDefs(LiveRange &LR, MachineBasicBlock &UseMBB, + SlotIndex Use, unsigned PhysReg, + ArrayRef<SlotIndex> Undefs); + + /// updateSSA - Compute the values that will be live in to all requested + /// blocks in LiveIn. Create PHI-def values as required to preserve SSA form. + /// + /// Every live-in block must be jointly dominated by the added live-out + /// blocks. No values are read from the live ranges. + void updateSSA(); + + /// Transfer information from the LiveIn vector to the live ranges and update + /// the given @p LiveOuts. + void updateFromLiveIns(); + + /// Extend the live range of @p LR to reach all uses of Reg. + /// + /// If @p LR is a main range, or if @p LI is null, then all uses must be + /// jointly dominated by the definitions from @p LR. If @p LR is a subrange + /// of the live interval @p LI, corresponding to lane mask @p LaneMask, + /// all uses must be jointly dominated by the definitions from @p LR + /// together with definitions of other lanes where @p LR becomes undefined + /// (via <def,read-undef> operands). + /// If @p LR is a main range, the @p LaneMask should be set to ~0, i.e. + /// LaneBitmask::getAll(). + void extendToUses(LiveRange &LR, unsigned Reg, LaneBitmask LaneMask, + LiveInterval *LI = nullptr); + + /// Reset Map and Seen fields. + void resetLiveOutMap(); + +public: + LiveRangeCalc() = default; + + //===--------------------------------------------------------------------===// + // High-level interface. + //===--------------------------------------------------------------------===// + // + // Calculate live ranges from scratch. + // + + /// reset - Prepare caches for a new set of non-overlapping live ranges. The + /// caches must be reset before attempting calculations with a live range + /// that may overlap a previously computed live range, and before the first + /// live range in a function. If live ranges are not known to be + /// non-overlapping, call reset before each. + void reset(const MachineFunction *mf, SlotIndexes *SI, + MachineDominatorTree *MDT, VNInfo::Allocator *VNIA); + + //===--------------------------------------------------------------------===// + // Mid-level interface. + //===--------------------------------------------------------------------===// + // + // Modify existing live ranges. + // + + /// Extend the live range of @p LR to reach @p Use. + /// + /// The existing values in @p LR must be live so they jointly dominate @p Use. + /// If @p Use is not dominated by a single existing value, PHI-defs are + /// inserted as required to preserve SSA form. + /// + /// PhysReg, when set, is used to verify live-in lists on basic blocks. + void extend(LiveRange &LR, SlotIndex Use, unsigned PhysReg, + ArrayRef<SlotIndex> Undefs); + + /// createDeadDefs - Create a dead def in LI for every def operand of Reg. + /// Each instruction defining Reg gets a new VNInfo with a corresponding + /// minimal live range. + void createDeadDefs(LiveRange &LR, unsigned Reg); + + /// Extend the live range of @p LR to reach all uses of Reg. + /// + /// All uses must be jointly dominated by existing liveness. PHI-defs are + /// inserted as needed to preserve SSA form. + void extendToUses(LiveRange &LR, unsigned PhysReg) { + extendToUses(LR, PhysReg, LaneBitmask::getAll()); + } + + /// Calculates liveness for the register specified in live interval @p LI. + /// Creates subregister live ranges as needed if subreg liveness tracking is + /// enabled. + void calculate(LiveInterval &LI, bool TrackSubRegs); + + /// For live interval \p LI with correct SubRanges construct matching + /// information for the main live range. Expects the main live range to not + /// have any segments or value numbers. + void constructMainRangeFromSubranges(LiveInterval &LI); + + //===--------------------------------------------------------------------===// + // Low-level interface. + //===--------------------------------------------------------------------===// + // + // These functions can be used to compute live ranges where the live-in and + // live-out blocks are already known, but the SSA value in each block is + // unknown. + // + // After calling reset(), add known live-out values and known live-in blocks. + // Then call calculateValues() to compute the actual value that is + // live-in to each block, and add liveness to the live ranges. + // + + /// setLiveOutValue - Indicate that VNI is live out from MBB. The + /// calculateValues() function will not add liveness for MBB, the caller + /// should take care of that. + /// + /// VNI may be null only if MBB is a live-through block also passed to + /// addLiveInBlock(). + void setLiveOutValue(MachineBasicBlock *MBB, VNInfo *VNI) { + Seen.set(MBB->getNumber()); + Map[MBB] = LiveOutPair(VNI, nullptr); + } + + /// addLiveInBlock - Add a block with an unknown live-in value. This + /// function can only be called once per basic block. Once the live-in value + /// has been determined, calculateValues() will add liveness to LI. + /// + /// @param LR The live range that is live-in to the block. + /// @param DomNode The domtree node for the block. + /// @param Kill Index in block where LI is killed. If the value is + /// live-through, set Kill = SLotIndex() and also call + /// setLiveOutValue(MBB, 0). + void addLiveInBlock(LiveRange &LR, + MachineDomTreeNode *DomNode, + SlotIndex Kill = SlotIndex()) { + LiveIn.push_back(LiveInBlock(LR, DomNode, Kill)); + } + + /// calculateValues - Calculate the value that will be live-in to each block + /// added with addLiveInBlock. Add PHI-def values as needed to preserve SSA + /// form. Add liveness to all live-in blocks up to the Kill point, or the + /// whole block for live-through blocks. + /// + /// Every predecessor of a live-in block must have been given a value with + /// setLiveOutValue, the value may be null for live-trough blocks. + void calculateValues(); + + /// A diagnostic function to check if the end of the block @p MBB is + /// jointly dominated by the blocks corresponding to the slot indices + /// in @p Defs. This function is mainly for use in self-verification + /// checks. + LLVM_ATTRIBUTE_UNUSED + static bool isJointlyDominated(const MachineBasicBlock *MBB, + ArrayRef<SlotIndex> Defs, + const SlotIndexes &Indexes); +}; + +} // end namespace llvm + +#endif // LLVM_LIB_CODEGEN_LIVERANGECALC_H |